AU2008293123B2

AU2008293123B2 - Method and device for removing the upper portion of a well

Info

Publication number: AU2008293123B2
Application number: AU2008293123A
Authority: AU
Inventors: Espen Alhaug; Lars Hovda; Erling J. Wiig
Original assignee: Claxton Eng Services AS
Current assignee: Claxton Engineering Services AS
Priority date: 2007-08-30
Filing date: 2008-08-27
Publication date: 2011-09-29
Anticipated expiration: 2028-08-27
Also published as: GB2463849B; NO327223B3; BRPI0816053A2; ZA201001615B; WO2009028953A1; GB2463849A; NO327223B1; AU2008293123A1; NO20074420L; MX2010002311A; GB201002387D0

Abstract

A method and device for removing the upper portion of a well (20) arranged in the ground, the upper portion of the well (20) including at least a portion of a casing (24) extending from the surface down into the ground (28), and, before the upper portion of the well (20) is removed, the casing (24) being cut at a distance below the surface, the method including the operations of: - arranging a cutting tool (2), which is arranged to cut the casing (24) at a distance below the surface, on a lifting tool (4) which is arranged to be connected to the casing (24) or a component (22) connected to the casing; - lowering the lifting tool (4) with the cutting tool (2) down towards the casing (24) until the lifting tool (4) abuts against the casing (24) or the component (22) connected to the casing; - connecting the lifting tool (4) to the casing (24) or the component (22) connected to the casing; - cutting the casing (24) by means of the cutting tool (2); and - lifting the severed portion of the casing (24) out of the ground (28) at least together with the cutting tool (2).

Description

METHOD AND DEVICE FOR REMOVING THE UPPER PORTION OF A WELL This invention relates to a method for removing the upper portion of a well. The invention also relates to a device for practising the method. s After a well in the ground has been permanently plugged, it is usual to remove at least the upper portion of the well from the ground at the surface. The surface may be consti tuted by a seabed. The well, which may typically be an independent one or belong 10 to a group of wells in a well frame, most often includes a composite casing, in which several casings of different di ameters are positioned one inside the other, and in which an nuli formed between the casings are normally filled with con crete. 15 A single or composite casing, which may also include other pipes, for example drive pipe, is termed a casing below. The casing typically extends into the ground from a wellhead which is located, in the case of a submerged well, above the seabed. 20 According to the prior art the upper portion of the well is removed by first placing a rig vessel above the well. The casing is cut below the seabed, typically by means of a me chanical cutting tool. After the casing has been cut, the 2 cutting tool is removed from the well, after which the lift ing equipment of the rig vessel is connected to the casing. The severed upper portion of the casing is then lifted out of the ground. s The prior art method presupposes the use of a relatively large vessel which is provided with drilling equipment, and is, because of repeated connection to the well among other things, relatively time-consuming. 1. One aspect of the invention provides a method for re 10 moving an upper portion of a subsea well arranged in ground below a seabed by use of a marine vessel, the upper portion of the well including at least a portion of a casing extending from the seabed down into the ground, and, before the upper portion of the well is is removed, the casing being cut at a distance below the seabed, the method comprising: - connecting a cutting tool, which is arranged to cut the casing at a distance below the seabed, to a lifting tool by use of a cable for 20 supplying abrasive fluid from the vessel, where the cable is movably passed through a guide pipe in the lifting tool, and where the lifting tool is arranged to be connected to the casing or a component connected to the casing; 25 - lowering the lifting tool with the cutting tool down towards the casing until the lifting tool abuts against the casing or the com ponent connected to the casing; - connecting the lifting tool to the casing or the 30 component connected to the casing; - cutting the casing by means of the cutting 3 tool to produce a severed portion of the casing; and - lifting the severed portion of the casing out of the ground at least together with the s cutting tool. In an embodiment the cutting tool can be moved relative to the lifting tool after the lifting tool has been placed on the casing or the component connected to the casing. In another embodiment the cutting tool is placed at a dis 10 tance below the lifting tool before the lifting tool abuts against the casing or the component connected to the casing. In an embodiment the cutting tool is secured to the casing before the cutting operation itself is started. Another aspect of the invention provides A device for re 1s moving an upper portion of a subsea well arranged in ground below a seabed by use of a marine vessel, the upper portion of the well including at least a portion of a casing extending from the seabed down into the ground, and, before the upper portion of the well is 20 removed, the casing being cut at a distance below the seabed by means of a cutting tool, wherein the cutting tool is connected to a lifting tool by a cable, for supplying abrasive fluid from the vessel, where the cable is movably passed through a guide pipe in the 2s lifting tool, the lifting tool being arranged to be connected to the casing or a component connected to the casing. In an embodiment, the cutting tool is arranged concentrically relative to the lifting tool, the connecting cable of the 30 cutting tool to the vessel extending via the lifting tool.

4 In the case of a hydraulic cutting tool using a so-called abrasive fluid, the connecting cable includes hoses for fluid flow and also necessary electrical cables. In some circumstances it may be advantageous for the lifting s tool to be provided with a mechanism which is arranged to move the cutting tool axially relative to the lifting tool. In an embodiment the lifting tool is provided with a locking mechanism for it to be connected to the casing or a component connected to the casing, typically formed by a wellhead. 10 Embodiments of to the invention provide a substantially sim plified procedure for the removal of the upper portion on a well, as several relatively time-consuming operations have been made redundant. The method and device are well suited for use on relatively small vessels with the resulting reduc is tion in cost. In what follows, is described an example of a preferred method and embodiment which is visualized in the accompanying drawings, in which: Figure 1 shows schematically a cutting tool and lifting tool 20 in accordance with the invention, which are being lowered down to a well on the seabed; Figure 2 shows the lifting tool abutting against a wellhead; WO 2009/028953 PCT/N02008/000302 Figure 3 shows the same as figure 2 but here the lifting tool is connected to the wellhead, the cutting tool is secured to the casing and the cutting operation has been started; and Figure 4 shows schematically the upper portion of the well lifted out of the seabed together with the cutting tool. In the drawings the reference numeral 1 indicates a cutting device including a- cutting tool 2 and a lifting tool 4, the cutting tool 2 having been positioned at a predetermined ver tical distance, for example in the order of ten metres, below the lifting tool 4. The cutting tool 2 is constituted by a hydraulic cutting tool, in which there is used an abrasive fluid, exiting under high pressure substantially radially from a rotating nozzle 6. The cutting tool 2 is supplied with fluid and electrical cur rent, for example for measuring equipment not shown, via a cable 8 extending from the cutting tool 2 up to a vessel not shown. The cutting tool 2 is provided with two securing de vices 10. The lifting equipment 4 is constituted by a wellhead tool, known per se, which is connected to the lifting equipment of the vessel, not shown, by means of a chain 12. The lifting tool 4 is provided with controllable locking dogs 14. The cable 8 of the cutting tool 2 extends via a guide pipe 16 through the lifting tool 4, the cutting tool 2 hanging con centrically below the lifting tool 4. A well 20, including a wellhead 22 and a casing 24, extends 5 WO 2009/028953 PCT/N02008/000302 from above the seabed 26 down into the ground 28. Here, the wellhead 22 forms the component connected to the casing 24, as it is described in the general part of the specification and in the set of claims. The wellhead 22 is provided with a connecting portion 30. The pipe bore 32 of the well 20 extends through the wellhead 22 and further within the casing 24. After the pipe bore 32 has been sealed at the bottom, the cutting device 1 is lowered down towards the well 20, see figure 1. The cutting tool 2 hanging below the lifting tool 4 is moved into the pipe bore 32 until the lifting tool 4, com plementarily fitting the connecting portion 30, abuts against the wellhead 22, see figure 2. The securing devices 10 are then urged against the pipe bore 32 to hold the cutting tool 2 in a fixed position relative to the casing 24. The lifting tool 4 is connected to the well head 22 by each of the locking dogs 14 being pivoted from its respective inactive position into its active position, in which the locking dog 14 grips under the connecting portion 30, see figure 3. The casing 24 is cut by means of abrasive fluid flowing at great velocity from the nozzle 6 against the casing 24 while the nozzle 6 is being rotated about its longitudinal axis at the same time. When the casing 24 has been severed, the cutting operation is stopped. The chain 12 is tightened, thereby pulling, by means of the lifting tool 4 and wellhead 22, the severed portion of the casing 24 out of the ground 28, see figure 4. The chain 12 may be replaced completely or partially by, for example, a wire, not shown. 6 7 It is emphasized that the casing 24 may be constructed as is mentioned under the prior art in the first part of the de scription. It is to be understood that, if any prior art publication is 5 referred to herein, such reference does not constitute an ad mission that the publication forms a part of the common gen eral knowledge in the art, in Australia or any other country. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise 10 due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the 15 invention.

Claims

1. A method for removing an upper portion of a subsea well arranged in ground below a seabed by use of a ma rine vessel, the upper portion of the well including s at least a portion of a casing extending from the sea bed down into the ground, and, before the upper por tion of the well is removed, the casing being cut at a distance below the seabed, the method comprising: - connecting a cutting tool, which is arranged 10 to cut the casing at a distance below the seabed, to a lifting tool by use of a cable for supplying abrasive fluid from the vessel, where the cable is movably passed through a guide pipe in the lifting tool, and where the lifting tool is arranged 15 to be connected to the casing or a component connected to the casing; - lowering the lifting tool with the cutting tool down towards the casing until the lifting tool abuts against the casing or the com 20 ponent connected to the casing; - connecting the lifting tool to the casing or the component connected to the casing; - cutting the casing by means of the cutting 25 tool to produce a severed portion of the casing; and - lifting the severed portion of the casing out of the ground at least together with the cutting tool. 2772116_1 (GHMatters) P83303 AU 9

2. The method in accordance with claim 1, w h e r e i n the cutting tool is moved relative to the lifting tool after the lifting tool has been disposed on the casing or the component connected to the casing. 5

3. The method in accordance with claims 1 or 2, w h e r e i n the cutting tool is placed at a distance below the lifting tool before the lifting tool is po sitioned on the casing or the component connected to the casing. 10

4. A device for removing an upper portion of a subsea well arranged in ground below a seabed by use of a ma rine vessel, the upper portion of the well including at least a portion of a casing extending from the sea bed down into the ground, and, before the upper por 15 tion of the well is removed, the casing being cut at a distance below the seabed by means of a cutting tool, wherein the cutting tool is connected to a lifting tool by a cable, for supplying abrasive fluid from the vessel, where the cable is movably passed through a 20 guide pipe in the lifting tool, the lifting tool being arranged to be connected to the casing or a component connected to the casing.

5. The device in accordance with claim 4, w h e r e i n the cable, extending from the cutting tool to the ves 25 sel, extends via the lifting tool.

6. The device in accordance with claim 4 or 5, w h e r e i n the cable is axially controllable within the lifting tool.

7. The device in accordance with anyone of claims 4 to 6, 30 w h e r e i n the lifting tool is connected to lifting equipment of the vessel and dimensioned to pull a sev 277211d_ 1(GHMattes) P03303.AU 10 ered portion of the casing out of the ground at least together with the cutting tool.

8. A method for removing an upper portion of a subsea well substantially as herein described with reference s to and as illustrated in the accompanying drawing.

9. A device for removing an upper portion of a subsea well substantially as herein described with reference to and as illustrated in the accompanying drawings. 2772110 I (GHMatters) P83303. AU